Apoptosis, i.e., programmed cell death, is a normal physiological process of a cell, which is characterized by DNA fragmentation, cytoplasma shrinkage, membrane change, and cell death without damaging neighboring cells. This process is regulated by a combination of various extracellular and intracellular signals. It allows a multicelluar organism to replace aged cells, control the cell number and the tissue size, and protect itself from cells that may lead to lethality. See, e.g., Li et al., Science 302, 1560-1563. Impaired apoptosis results in excessive levels of unwanted cells, which, in turn, cause disorders such as cancers, autoimmune diseases, immunodeficiency diseases, reperfusion injuries, and neurodegenerative diseases. Therefore, apoptosis-inducing compounds are drug candidates for treating these disorders.